Showing papers on "Magnetic circuit published in 1971"

A New Method to Eliminate AC Harmonic Currents by Magnetic Flux Compensation-Considerations on Basic Design

Abstract: A new method of eliminating ac harmonic current is proposed, which is based on the principle of the magnetic flux compensation in a transformer core. By means of the new method, abnormal harmonics as well as normal harmonics can effectively be dealt with. Considerations on the basic design of the new method are given.

Analysis of the Efficiency of Thin‐Film Magnetic Recording Heads

Abstract: Equations for the flux, magnetic field, and current distributions in a single‐turn planar magnetic recording head are derived making the assumption that the magnetic material has constant permeability. These equations are solved in the frequency domain and an expression is given for the head efficiency in terms of the head dimensions, permeability, and frequency.

Linear motors with transverse flux

Abstract: The paper describes a new family of linear machines which may have advantage in applications where the pole pitch is very much greater than the machine width. Compared with the more usual kind of linear motor, in which the magnetic flux lies largely in planes which are parallel to the direction of motion, the new machines, have flux paths lying transversely to this direction. This shortens the magnetic circuit and reduces the weight of steel core needed in narrow machines of large pole pitch. Two experimental machines are described which illustrate the techniques needed in construction, and some initial calculations on possible weight gains are included.

Tool monitoring apparatus

Abstract: Apparatus for monitoring the condition of a tool and for detecting the improper operation thereof. The apparatus utilizes a magnetic circuit formed of a first low reluctance portion and a second high reluctance portion having a pulsating magnetic flux induced therein. In normal operation, the tool to be monitored is adapted to be positioned within and substantially bridge the high reluctance portion, which preferably comprises an air gap, and become a part of the circuit thus

Current measuring and automatically resettable fault indicating means

Abstract: A capacitor is charged through a capacitive coupling to a high voltage alternating current electric power conductor and is discharged when the charge reaches a predetermined value to reset fault indicator that previously had been operated by flow of fault current in the conductor. The magnetic circuit employs a demagnetizable low coercive force core in the form of a bifurcated yoke or a ring having magnetizing windings energized on discharge of the capacitor. A manually resettable fault indicator employing a demagnetizing winding on a low coercive force ring also is disclosed.

Electromagnetic induction apparatus

Abstract: Electromagnetic induction apparatus for high-voltage, high-power operation, using a compact interrupted magnetic circuit whose materials and geometry are so designed as to confine magnetic flux to the compact geometry associated with the magnetic circuit, to confine operating electric currents to windings which cooperate in forming the magnetic circuit, and to distribute both normal and transient voltages quickly and evenly along both the winding and the magnetic circuit so that the electric field strength of the system is maintained high. The apparatus may be applied to either the transformer or the reactor function, but in either event the purpose and advantages of the invention generally relate to so-called large power operation (above ten megavolt amperes) at voltages in the EHV and UHV levels. EACH ODDDDZ0Dsre etdDDD)s nDDDE

Write-process study on integrated magnetic heads

Abstract: The write field of multilayered integrated heads has been computed avoiding the usual assumptions that the head contour is an equipotential surface, by starting from the effect of the coil field on the magnetization of the layers. The magnetic analysis assumes that the magnetization of each layer curls near the head boundary, and it is shown that this curling significantly affects the write-field distribution. Experimental measurements are in good agreement with these theoretical results, and it is shown that integrated heads produce a write field whose magnitude is comparable to that of classical heads.

Deposited latched junction circulator having magnetic flux return paths

Abstract: A latching ferrite circulator utilizing deposited ferrite layers and operable without the requirement of a permanent magnet. A pair of separated ferrite layers respectively include a microstrip transmission line circuit and a ground plane on faces which oppose each other. The microstrip transmission line comprises at least one hub circuit portion and a plurality of circuit arm portions. At least two coplanar ferrite elements are deposited between the microstrip transmission line circuit and the ground plane. One ferrite element comprises the circulator element and is placed contiguous with the hub while the other ferrite element comprises a magnetic return path member which is located a predetermined distance from the circulator element. A latching conductor is located generally in the plane of the microstrip circuit intermediate the two ferrite elements so that when a DC current pulse is applied to the latching conductor, a closed magnetic circuit loop is provided through the two ferrite elements and the ferrite layers containing the microstrip circuit and the ground plane.

Electric hot water circulating pump with motor having an axial air gap

Abstract: In an electric pump used for the circulation of hot water the inductor of the moor is formed by a stator of the front type and the armature consists of a fixed magnetic part and a movable disc of material having a high conductivity keyed onto the end of the shaft, onto the opposite end of which the pump impeller is keyed. By separating in this manner the electrical circuit of the rotor from the magnetic circuit the axial thrust is eliminated.

Magnetic bearings for spacecraft

Abstract: Magnetic bearings have been successfully applied to motorized rotor systems in the multi-kilogram range, at speeds up to 1200 radians per second. These engineering models also indicated the need for continued development in specific areas to make them feasible for spacecraft applications. Significant power reductions have recently been attained. A unique magnetic circuit, combining permanent magnets with electromagnetic control, has a bidirectional forcing capability with improved current sensitivity. The multi-dimensional nature of contact-free rotor support is discussed. Stable continuous radial suspension is provided by a rotationally symmetric permanent magnet circuit. Two bearings, on a common shaft, counteract the normal instability perpendicular to the rotational axis. The axial direction is servoed to prevent contact. A new bearing technology and a new field of application for magnetics is foreseen.

Low power magnetic circuit breaker

Abstract: Disclosed is a circuit breaker which may be operated on relatively low power. It comprises a polarized relay having a spring-biased armature rotatable to trip a conventional circuit breaker toggle. The armature is released by the flux from a low power coil bucking out the polarizing flux from a permanent magnet. The breaker is disclosed in overvoltage protection and/or undervoltage protections circuits, as well as in a ground fault interruption circuit, and may be used with a conventional breaker overcurrent coil and toggle trip assembly.

Apparatus for determining the permeability of a non-magnetic medium

Abstract: A plurality of non-ferromagnetic bodies having a poor conductivity and different magnetic permeabilities are positioned in a gap formed in a magnetic circuit biased by a DC magnetic flux. The bodies are displaced relatively within the gap to cause a change of the flux, thereby providing alternate outputs in the coil. These alternate outputs are proportional to the difference between the magnetic permeabilities of these bodies. If one body is a sample of known permeability and the other body is sample of unknown permeability to be measured, the unknown permeability of the sample to be measured may be determined instantaneously by suitably processing or evaluating the alternate output or outputs.

Calculation of the Signal Voltage Induced in a Toroidal Proton-Precession Magnetometer Sensor

Abstract: The signal EMF induced as a function of time in a proton-precession magnetometer sensor of toroidal shape with an elliptical cross-sectional area is calculated in terms of the magnetic properties of the sensor fluid, polarizing current, orientation of the sensor with respect to the direction of the ambient magnetic field, and geometric proportions of the sensor. It is assumed that the sensor is in a uniform ambient magnetic field; the polarizing current is reduced to zero in a time that is short compared to the period of the Larmor precession of the nuclear magnetic moments in the sensor fluid; the nuclear magnetic moments do not interact; and no significant current flows in the sensor winding during the relaxation process in which the EMF is measured. In the specific case that the sensor winding fills the toroid window and that the polarizing supply is a constant voltage source, the calculations permit a simple comparison of variously proportioned sensors in terms of the signal EMF amplitude.

Apparatus for measuring the differences in magnetic susceptibilities of gases

Abstract: Apparatus for measuring the difference in magnetic susceptibility of a sample gas and of a reference gas, the reference gas having particular, constant susceptibility; a magnetic circuit has at least one measuring gap with a plane or line of symmetry as to the magnetic field in the gap or of the gaps; a test body including two chambers of symmetrical configuration in relation to each other, one chamber provided for the reference gas, the other for the sample gas is resiliently suspended in the gap so that for zero reaction force the test body is symmetrically disposed in the gap or gaps with reference to the plane or line of symmetry (equilibrium position) when the contents of the chambers have equal magnetic susceptibility whereby the body extends in zones of magnetic inhomogeneity with similar volume as to portions of the body defining the two chambers.

Computation of Eddy Currents, Shielding and Transient Forces in Power System Equipment by the Method of Images

Abstract: The magnetic effects of induced eddy currents in thin conducting sheets are analyzed by means of moving current images and by an electrical circuit analogy. The methods are applied to practical power system equipment problems such as shielding and the calculation of conductor short circuit forces.

Method for adjusting the strength of high energy magnets

Abstract: A high capability, oriented, ceramic permanent magnet is assembled into the magnetic circuit in which is intended to function, and its strength is reduced by demagnetization until it provides the desired flux density for the circuit. This demagnetization is accomplished by encircling the magnet with a demagnetizing coil and applying current pulses to the coil. Control over the degree of demagnetization is achieved by orienting the demagnetization field perpendicular to the direction of polarization of the magnet.

Sensing and control device for electric motor-starting circuits

Abstract: A versatile sensing transformer for actuating a semiconductor gate in the starting circuit of an electric motor, comprising a U-shaped magnetic base, inductive coupled primary and secondary windings mounted on the base in coaxial relation to each other and electrically connected to the motor and the semiconductor gate, an adjustable and removable magnetic core threaded into the base and projecting axially of the cores, and a magnetic cap bridging the open end of the base to form a complete magnetic shell, the cap being adjustable toward and away from the coils and core to vary the overall reluctance of the magnetic circuit.

A comprehensive circuit model for the electromechanical/Acoustic transducer

Abstract: A comprehensive circuit model is derived for the electromechanical transducer using an electromagnetic gyrator to link the electric and the magnetic circuits and a magnetomechanical gyrator to link the magnetic and the mechanical circuits. The unified model permits evaluation of the effect of the system parameters on overall operation, particularly the parameters of the magnetic circuit. The loudspeaker is discussed as a particular example although the theory can he extended to other electromechanical devices.

Improvements relating to electro-magnetic tripping devices

Abstract: 1,236,916. Electromagnetically tripped switches. A. REYROLLE & CO. Ltd. 3 Sept., 1968 [5 June, 1967], No. 25856/67. Heading H1N. A polarized holding electromagnet having a spring-biased armature releasable to act on a circuit-breaker trip mechanism, has a yoke structure of symmetrical rectangular form affording duplicated magnetic circuits, one on either side of a central elongated core member which is common to both magnetic circuits and on which two spaced series trip coils are wound. The armature 30 is rectilinearly movable and is ' held, by flux from permanent magnets 19, 20, in engagement with faces 26 of two rectangular section polepieces 21 to bridge air gaps 29 in the duplicated magnetic circuits on either side of the core 13 which also houses the armature biasing spring 35. Air gaps between the polepieces 21 and magnetic end pieces 16 are set by non-magnetic shims 24. The housing 10 is dust-proofed by a diaphragm 41 secured around a guide sleeve 37 for the extension spindle 31, 36 of the armature which has a spring-loaded button 40 to allow for overtravel in resetting of the trip mechanism (not shown). The permanent magnets may be magnetized after assembly in the housing 10 of the electromagnet by temporarily connecting the coils 14, 15 in parallel and in opposition (Fig. 5, not shown). In an alternative arrangement (Figs. 6 to 8, not shown) soft iron shunts are provided so as to prevent demagnetization of the permanent magnets during an initial current surge in the coils 14, 15.

Unipolar double inductor dynamo

Abstract: A unipolar double inductor dynamo having an anti-inductor winding for eliminating the axial flux produced by the inductor windings in an armature or stator by generating a high antiinductor flux and consequently a high saturation in the magnetic circuit of the anti-inductor, the inductor and anti-inductor rotating in opposite directions.

Asynchronous machine having an open magnetic circuit

Abstract: Asynchronous machine having an open magnetic circuit comprises a field member including central and end sections. The central section is fully wound with a polyphase winding and a monophase winding. The end sections are unwound or partially wound with a monophase winding. The central section has an odd or fractional number of poles and the length of the end sections are from zero to 1 pole pitch long.

Meter and method of calibration

Abstract: A D''Arsonval type moving coil meter with linear scale deflection characteristics. The magnetic circuit of the meter is such that the sum total of flux which cuts the coil is the same for any operative position of the coil. Correspondingly, angular deflection of the coil is in direct proportion to the current in the coil. The magnetic circuit includes a magnet having fixed locating surfaces thereon which cooperate with fixed locating surfaces on a yoke. This locating arrangement assures that the sum total of flux which cuts the coil is the same for any operative position of the coil and further assures repeatable accuracy in successively assembled meters. The meter is calibrated by magnetizing the magnet to obtain full scale deflection when rated current is applied to the meter terminals. Where a calibrating resistor is used, the resistor is connected to the meter prior to calibration with the result that accuracy of the meter is assured without the need for using a precision resistor.

Measurement of losses in saturated solid magnetic cores

Abstract: A new method of measuring the losses in saturated solid magnetic cores subjected to alternating magnetization is described. The method is based on the measurement of an alternative Poynting vector in the region between the surface of the iron core and the magnetizing winding. The two constituent components of this power-flow vector are the partial electric field and the magnetic field. A brief description of suitable probes for measuring these two field components and the associated measuring circuit is given. Loss measurements are made on two cores, a long rod, and a toroid; the results are compared with those calculated using analytical and numerical methods and also with those predicted by linear electromagnetic theory.

Roll for displacement of bar-like products

Abstract: A roll for transporting elongated ferro-magnetic bar-like products, includes a series of axially aligned magnetizing coils, and a magnetic circuit around each coil. Each magnetic circuit comprises an annular magnetic core within the coil, magnetic elements extending from the core on each side of the coil, and ring means surrounding the coil. The ring means includes a non-magnetic portion of less width than that of the magnetic portion. The coils are supplied with direct current, and the roll is mounted on a non-magnetic shaft.

Electromagneti pumps for liquid metals

Abstract: A gapless and an air-gap magnetic circuit are separated by a clearance which accommodates a straight conduit conveying a liquid metal. The air-gap magnetic circuit is the multipole core of an A.C. electromagnet and serves to establish a magnetic field in the liquid metal. The gapless magnetic circuit is a polyphase transformer with single-turn secondary windings formed by the liquid metal and a conductor enveloping the transformer core. The gapless magnetic circuit induces an electric current in the liquid metal. The magnetic field and the electric current interact to produce an electromagnetic head.

A Method for Simulating Electric Machines

Abstract: In this paper a method is given to simulate electric machines on analog or digital computers. The windings in both axes of a generalized electric machine, considered as n coupled windings, are first transformed into Pi-equivalents, whose components are closely related to the actual magnetic circuits. The motional electromotive forces being then included, it is possible to draw a signal flow-graph which represents the machine to be simulated. This signal flow-graph leads directly to computer set-ups without differentiators. Also, the technique described in this paper is especially useful when using digital programs since the signal flow-graph does not contain any algebraic loop. It can therefore be used to write a digital program using any available simulation language.

Receiver for centralized controlling apparatus

Abstract: A receiver for a centralized controlling apparatus is used for switching a load at a given remote location upon the receipt of a transmission of a specific frequency signal from a station through a transmission or distribution line. In the receiver, a serially connected resonance coil and condenser are provided and resonated by the specific frequency signal transmitted through the transmission or distribution line. A mechanical resonator is vibrated in accordance with the resonance of the resonance coil and condenser to thereby change the magnetic flux in a magnetic circuit and to provide an induced voltage in a coil for detecting the specific frequency signal. A switching element is triggered by the induced voltage to actuate a differential relay and to thereby switch a load circuit.

An Inexpensive, Large Bandwidth, Precision D. C. Current Transformer for Stabilised Magnet Power Supplies

Abstract: Precision D. C. current transformers for magnet power supplies are generally based on:-either (a) the "zero flux", 2nd harmonic modulator principle, or (b) the series connected transductor (Kraemer) circuit. Solution (a), while capable of the highest precision, is relatively costly and characterised by large time constants. Solution (b) while much cheaper by contrast, suffers from a high ripple voltage level and from ratio errors which stem from the magnetic uncoupling of primary and secondary windings when the cores saturate simultaneously twice per cycle of the excitation supply. The Brentford/Hingorani circuit, described in the paper, by a simple circuit change eliminates the uncoupling error and considerably reduces the ripple. A further small component addition reduces the residual ripple to negligible amplitude. Very large bandwidths (for pulsed supplies) are easily obtainable without detriment to stability. The paper describes some second and third order error sources and their elimination and concludes with a brief description of the design of D. C.C.T. used for the 101 stabilised power supplies employed in the beam transfer lines of the Intersecting Storage Ring installation at C.E.R.N., Geneva, Switzerland. Measured performances on this installation show many of the power supplies capable of half-hour stabilities of one or two p.p.m. in the presence of environmental deviations much greater than those usually experienced in similar installations.